Six in ten people in the United States are overweight, with a third crossing the boundary into obesity. The extra weight leads to at least 100,000 deaths annually. Obese people are at a much higher risk for heart attacks, strokes, diabetes, arthritis and some cancers.

Doctors call people obese if their weight in kilograms is more than 30 times bigger than their height in meters squared. This is known as a high body mass index, or BMI.

Even kids are getting fatter. Nineteen percent of children between the ages of 6 and 11 are overweight, up from 4% in the 1970s. Doctors are turning to intensive behavioral therapy to try to keep these children from gaining more weight.

The economic cost of all this extra fat is immense. Direct medical costs are easiest to calculate, coming in at $93 billion, or 9 percent, of our national medical bill. But there are other costs as well that are harder to pin down.

"There's a tremendous social cost to obesity," says David Allison, an obesity researcher at the University of Alabama at Birmingham. "Obese people are less likely to be given jobs, they're waited on more slowly, they're less likely to be given apartments, they're less likely to be sent to college by their parents."

Obese people miss more work, costing employers something on the order of $4 billion. Because people are fatter, airlines spend more on jet fuel, and the obese themselves spend more on gas. But these tend to be hidden from consumers themselves. Many researchers believe that it's actually cheaper, in our fast-food society, to eat a high-fat, high-calorie diet than it is to stay slim. Supersizing a meal at McDonald's, Burger King or Kentucky Fried Chicken costs a consumer only 67 cents out of pocket. But after health costs and the price of extra gasoline are factored in, for some people, the price of the meal may have been effectively doubled.

Financial incentives
Eric Finkelstein, a health economist at the nonprofit RTI Institute who has done extensive work with the Centers for Disease Control to measure the health costs of obesity, worries that there are no incentives for employers to deal with the expanding waistlines of their workers.

The reason: The average employee only stays at a job for 4.5 years, and it actually takes far longer for health problems due to being overweight to emerge. Unless a company holds onto its employees for decades and gives them great health benefits — such as, say, General Motors — it won't reap the benefits of helping employees lose weight.

Moreover, Finkelstein says, employers never pay most obesity costs. Instead, they get passed onto the government through Medicare. Finkelstein will lay out this argument in a forthcoming article in the North Carolina Medical Journal.

"Obese people cost lots of money," he says. "But young obese people really don't cost much at all. Why should an employer invest in obesity prevention to save Medicare money?"

To make matters worse, Finkelstein says, there is very little employers could do to prevent obesity in a world where people aren't stuck at a single job. He estimates that 9 percent of Americans are eligible for bariatric surgery, in which the stomach is tied off to make it smaller. (The procedure is probably best known for slimming celebs such as weatherman Al Roker and singer Carni Wilson.) But even that would cost most employers more than they would save.

One speculative solution: In surveys, people have said that they would be willing to lose 10 pounds — and keep it off — if they were paid $225. If people can't see the savings of staying slim, maybe the solution is to make their pocketbooks heavier.